1. Field of the Invention
The present invention relates to orthodontic appliances for the correction of misaligned teeth. More particularly, the present invention relates to removable orthodontic aligners with a plurality of springs for correcting individual misaligned teeth.
2. Description of the Prior Art
Removable orthodontic appliances have been used since the beginning of modern orthodontic therapy. Dr. Edward H. Angle, considered the Father of Orthodontics, discussed removable orthodontic appliances in the seventh edition of his classic textbook entitled MALOCCLUSION OF THE TEETH, published in 1907. However, the impetus for the evolution of removable orthodontic appliances essentially results from the work of two other men: Dr. C. A. Hawley and Dr. George Crozat.
In order to discuss and describe the invention with accuracy and clarity using dentofacial terminology, a number of definitions will now be provided. In referencing the teeth, the anterior or front teeth of either jaw include the central incisors, which are the two teeth typically foremost in the mouth; the lateral incisors, which are adjacent the central incisors; and the cuspids or canines, which are adjacent the lateral incisors. The posterior or back teeth of either jaw include the bicuspids or premolars, which are posteriorly adjacent the cuspids and naturally in pairs, and the molars. For referencing the various areas of the dentition relative to the mouth, labial refers to that portion of the tooth directed toward or relating to the lips, lingual refers to the tongue, buccal refers to the cheeks, gingival refers to the gums, and palatal refers to the palate. For referencing specific areas of teeth, the occlusal surface is the top surface of the crown of a tooth of one jaw opposing and normally contacting the corresponding tooth of the other jaw; additionally, the mesial portion or surface is the portion of a tooth nearer to the middle or bilateral center of the jaw or mouth, while the distal portion or surface is the portion of a tooth farther from the middle of the jaw. Accordingly, it can be said that each tooth has a labial or buccal surface, a lingual surface, an occlusal surface, a mesial surface, and a distal surface.
Returning to the development of modern orthodontics, in 1919 Dr. Hawley reported the development of a simple and efficient removable retaining appliance that he had developed during the preceding dozen or so years of his clinical practice. This removable retaining appliance, now known as the Hawley retainer, remains essentially unchanged since that time and is still commonly used today. The Hawley retainer was primarily designed as a retaining device and was not intended for anything other than minor tooth movement. However, key components of the Hawley retainer, the labial wire and the acrylic body, provide the foundation on which many modern day appliances are based.
A year after Dr. Hawley's disclosure, Dr. Crozat reported the use of removable appliances as a means of straightening misaligned teeth. His appliance consisted of wires both on the lingual side and on the labial or the buccal side of the teeth. Dr. Crozat attempted to push forwardly or to rotate a tooth through the use of lingual wires. Although Dr. Crozat's appliance caused expansion of the buccal segments, it could be used to improve the alignment of the anterior teeth if space were sufficient.
As orthodontics progressed in sophistication, the concept of growth guidance for children became a part of orthodontic services. In addition to conventional braces, many removable appliances with various spring and wire designs became available. The goal of these appliances was to influence jaw growth rather than to align the teeth individually. These removable appliances are commonly referred to as "functional appliances" and include Activators, Bionators, Frankels, and Sagittals. As these devices are primarily designed to influence jaw growth, they are neither effective in adult orthodontic treatment nor capable of efficiently and predictably aligning crooked teeth.
There are various designs of orthodontic devices known as spring-aligner appliances. These appliances are designed to correct and then to retain minor incisor irregularities such as simple crowding and rotation. For example, if relapse has occurred following orthodontic treatment, the spring aligner may be use to make minor corrections. To construct this type of appliance, the teeth to be aligned are cut off a plaster dentition model and moved into the desired portion. The appliance is then fabricated over the model of repositioned teeth. Orthodontic movement is accomplished by labial and lingual acrylic plates or fittings that have been formed over stainless-steel wire fitted on the repositioned model. These types of appliances cannot be adjusted following fabrication to change any individual tooth position. If different or additional movement is desired, a new appliance must be made. Further, only minor changes can be accomplished by spring aligners as movement of the teeth to be aligned is effected by pressure from the acrylic fitting, not wires directly contacting the teeth. Accordingly, these appliances are not particularly effective for tooth movement and are otherwise highly labor intensive in their fabrication.
Most retainers that are used to align teeth are designed with an acrylic palate or a lingual plate, a labial wire, and a myriad of different posterior retaining clasps to secure the appliance to the posterior teeth. A long recurved flexible spring imbedded in the acrylic fitting usually provides the force to move the teeth. One drawback of such design is that the recurved spring may unexpectedly deflect, thereby changing the intended force direction. Further, if the recurved spring is placed against an incisor which is positioned too far backward, the spring will be ineffective if it distorts vertically, sliding up the lingual surface toward the incisal surface of the incisor. In addition to these drawbacks, it is difficult to pinpoint the pressure to an exact position on the tooth to be moved.
A specific example of an orthodontic appliance which uses springs to move teeth is U.S. Pat. No. 4,026,023 granted to Fisher in 1977. Fisher teaches a T-shaped spring having a vertical portion and a horizontal portion which abuts a tooth. The vertical portion has a pair of spaced tag portions at its lower end for attaching to the orthodontic appliance and a pair of spaced parallel arm portions. The horizontal portion is formed by a pair of oppositely positioned, rounded loop portions with a bridge portion therebetween. This spring design has a drawback in that the fabrication thereof requires multiple bends to form the horizontal and vertical portions. Further, the amount of wire used to form a single spring is substantial as the vertical portion requires a doubling up of the wire, which doubled-up construction also limits the mobility of the spring. Such complicated fabrication and noneconomical use of material are considered to be undesirable aspects of many recently proposed orthodontic devices.
Following my review of many years of development of orthodontic appliances, it has become increasingly obvious to me that an unfulfilled need exists for a removable orthodontic appliance which aligns the anterior teeth while not altering the posterior teeth, an appliance which is easy to construct and which effectively repositions teeth with novel springs. This need has arisen from the fact that a considerable market for such an appliance is driven by a large segment of the population which has crooked or spaced front teeth and very acceptable back teeth. However, despite the efforts of skilled practitioners in the orthodontic arts, the need for such a removable orthodontic appliance remains unfulfilled up to the present.